Don't think it really makes sense to suggest the Formula Device for this task.

You can definitely control the tempo with that thing and do some weird crap, but you can't really do what delt is asking for. You cannot easily nudge the tempo up or down by some small amount this way, without applying the device's output in a continuous fashion, which you'd be better off doing via graphical automation anyway.

I remember I had a hard time trying to realistically play a classical piano piece in Renoise, it all boiled down to getting the tempo changes right, it had to slow down and speed up gradually along the way. Since I had to operate in absolute values, if suddenly it was apparent that tempo slide was not right, I had to resequence the whole tempo effect block in the pattern. Having to handle hex values did not make things any easier.

It took many hours to do right a piece 3 or 4 minutes long. If indeed I could do something like ...TZ01 ...TZ00 ...TZ12...TZ00 ...TZ00(where TZ00 would mean to keep sliding the tempo) it might have been alot easier to adjust things.

Yeah, same here.... years ago for a certain piano piece, in impulse tracker it took a few minutes to add the timing inflexions i wanted using T1x / T0x ....when a few years later i wanted to do a better version of this piece in renoise, it took me considerably longer to calculate all those tempos to absolute values...

...and now, what if i decide the piece sounds better, say, 2 or 3 bpm slower or faster? It would take me hours to change all those values in every pattern!!

...and now, what if i decide the piece sounds better, say, 2 or 3 bpm slower or faster? It would take me hours to change all those values in every pattern!!

Advanced edit, subtract or add 2/3 assuming you insert Txx commands in their own effect column and don't mix it with other commands in just one column.I would recon it takes less than 5 minutes to accomplish that change. Specially if you tick the "selection in song" option.

Yeah, that would work for changing all of them afterwards.... IF i remember to dedicate one effect column for -only- tempo changes.

Though (1) it wouldn't be as clean to have all those "hard-coded" values lying around in the pattern data, and (2) it would still be much more tedious to add small timing inflexions, than just having ZT0x / ZT1x for add/subtract tempo. (of course there's automation curves, but ....)

Yeah, that would work for changing all of them afterwards.... IF i remember to dedicate one effect column for -only- tempo changes.

Though (1) it wouldn't be as clean to have all those "hard-coded" values lying around in the pattern data, and (2) it would still be much more tedious to add small timing inflexions, than just having ZT0x / ZT1x for add/subtract tempo. (of course there's automation curves, but ....)

I'm not sure how much the tempo fluctuation range should be and how frequent:You could also simply use an LFO on the tempo parameter. If you need it to raise or drop 2/3 bpm, you can just change the offset, it will then be arranged with just one slider. Just note i'm here trying to help you out now, i'm not trying to convince you to drop the time-slide idea.

Like i said recently in another thread.... you can't go wrong with having the functionality, vs. not having it... especially something that would be so trivially simple to implement, and would be immensely useful (at least to me) - currently ZT0x and ZT1x are simply ignored.